Many search engine services, such as Google and Yahoo!, provide for searching for information that is accessible via the Internet. These search engine services allow users to search for display pages, such as web pages, that may be of interest to users. After a user submits a search request (i.e., a query) that includes search terms, the search engine service identifies web pages that may be related to those search terms. To quickly identify related web pages, the search engine services may maintain a mapping of keywords to web pages. This mapping may be generated by “crawling” the web (i.e., the World Wide Web) to identify the keywords of each web page. To crawl the web, a search engine service may use a list of root web pages to identify all web pages that are accessible through those root web pages. The keywords of any particular web page can be identified using various well-known information retrieval techniques, such as identifying the words of a headline, the words supplied in the metadata of the web page, the words that are highlighted, and so on. The search engine service identifies web pages that may be related to the search request based on how well the keywords of a web page match the words of the query. The search engine service then displays to the user links to the identified web pages in an order that is based on a ranking that may be determined by their relevance to the query, popularity, importance, and/or some other measure.
Search engine services typically track all search requests submitted by users by storing the search requests and their corresponding search results in a search log. A search log also includes an indication of a date and time associated with the search request (e.g., the time the search request was submitted). For example, when a user submits the search request “earthquake tsunami,” the search engine service identifies matching documents (e.g., web pages), ranks those documents, and displays to the user links to the documents ordered based on the rank of the documents. The search engine service may also add an entry to the search log that contains the search request “earthquake tsunami” and the links of the search result.
Search logs may also be generated by search systems that are unrelated to web page searching. For example, a web site of a company that sells the company's products may allow users to search for products of interest using search requests. When a user submits a search request, a search system of the web site may search an electronic catalog of the products to identify products that best match the search request. The web site then generates a web page that identifies the matching products and provides that web page to the user. The web site may maintain a search log of the product search requests. As another example, a web site of a provider of a database of patents may provide a search system to search the content of the patents. When a user submits a search request, the search system of the web site searches the database of patents to identify the patents that best match the search request. The web site then presents those patents to the user. The web site may also maintain a search log of the patent search requests.
Because the search logs contain the search requests of users, they may contain valuable information on what is currently of interest to users. For example, when a current event occurs, users of a search engine may submit search requests relating to that event in hopes of locating information about the event. If the event is an earthquake, then the users may enter search requests such as “seismograph,” “Richter scale,” “tsunami,” and so on. Although techniques have been developed to identify keywords whose popularity is increasing rapidly, these techniques may not provide an effective and easy-to-calculate measure of this increase.